I would agree that the SDCC exclusive will be Ahab. Scott Allie said at ECCC that the Ahab figure would be premiering in July, which he thought was kind of unfortunate given that the comics don't start until September. NECA told me on Twitter that they themselves don't know too much about "Fire and Stone" yet, but I've got my fingers crossed that we get a Galgo, mutant Elden, and maybe even adult Deacon figure.
As far as other exclusives, hopefully we get some posters of Palumbo's and Gist's covers. I would love to have a medium sized copy of Palumbo's ECCC mural on my wall.
This is a stretch, but maybe we'll eventually see some kind of "The Art of Fire and Stone" art-book. Dark Horse has talked a bit recently about how much success they've had doing those for their video game properties, so who knows.
I think from what we've seen so far, I wouldn't be too afraid of this being as bad as TWW. I just want a story that feels like it matters to this universe.